I will aerate just about any time. I prefer nice just mowed turf that was watered the night before but I will aerate in the rain in a heart beat. Now if it is pouring and I am rutting that is where I draw the line. No ruts roll on. It is definitly a mess though on the wheels of aerator and your shoes.

Any work on turf in the rain and in wet conditions damages the turf.You will be compacting the soil as you aerate it,you will make a muddy mess and it wont do the lawn a whole lotta good cuz your plug holes will fill up with surrounding soil and it's just not good lawncare .

Don't do it mate. it will change the profile of the soil, thus creating more problems. i agree that hte soil should be moist, just b careful

Not sure what you are meaning profile of soil? There is no differance from aerating on a sunny day and then turning on the sprinklers as oposed to aerating in the rain.
If you mean profile in that you are taking a solid surface and pulling thousand of little cores? That is what aeration is.
We aren't talking about a drenched piece of turf where you are leaving ruts every where. Just rain.